[ExI] Neutrino interaction web

[Adrian Tymes]

On Fri, Mar 4, 2011 at 2:50 AM, Anders Sandberg <anders at aleph.se> wrote:
> Remember that neutrinos and quarks are as far as we know point particles,
> and the neutron is about 2*10^-16 m across. Most of it is empty space.

Another wrinkle, then.  The point was to fill in the empty space - and as
difficult as doing it with neutrons would be, doing it with the quarks that
make up neutrons would be even harder.

> Worse, if two particles have no interactions allowed

Neutrons and neutrinos do interact gravitationally and through the strong
nuclear force, to my understanding.  Just not electromagnetically.

On Fri, Mar 4, 2011 at 5:54 AM, Richard Loosemore <rpwl at lightlink.com> wrote:
> I wouldn't go that far :-), but the collision cross section for neutrinos is
> estimated to be such that if you want to catch a significant fraction of
> them you need *roughly* a 1 light-year thick sheet of lead.

Ah, but that's with atoms.  All that empty space.

> So, I don't see any problem with Adrian's ideas except that you need to take
> a 1 light-year thick sheet of lead then compress it to make a thin sandwich
> that we can install in orbit, to collect the sun's neutrino output.
>
> Shouldn't be too difficult.  Bit of engineering, is all.

Neutron stars are compressed matter of that sort.  Except they're balls, not
sheets, and unless you've got a way to get them to spread out despite their
own gravity pulling them into a ball is the tricky part.